A method of manufacturing an absorbent article such as a pants-type diaper, a sanitary napkin and a panty liner is implemented in an assembly line. For instance, a continuous web including a continuum of top sheets and a continuum of back sheets to form absorbent articles is conveyed under tension in a web conveyance direction by a conveyor. Then, component members such as a gather (elastic member) and a waterproof film are placed on the web being conveyed under tension in the web conveyance direction.
In some cases, a side edge portion of a web during conveyance may be misaligned in a cross direction (a web width direction) perpendicular to a web conveyance direction. To address this problem, there is a known conveyor configured to adjust the passing position where a side edge portion of a web passes during conveyance (see PTL 1, for example). Specifically, the conveyor includes nip rollers, an actuator and a sensor as a detection mechanism.
The nip rollers include two rollers configured to hold at least one of side edge portions of a web. The nip rollers are each rotatable about one end of a shaft in a plan view of the web. The actuator is coupled to the nip rollers through an arm and the like, and rotates the nip rollers. The sensor detects the passing position of the side edge portion of the web after passing between the nip rollers.
In the conveyor thus configured, when the sensor determines that the passing position of the side edge portion of the web is misaligned from a predetermined position, the nip rollers are rotated by the actuator to guide the side edge portion of the web outward or inward in the web width direction. Thereby, the conveyor can adjust the passing position of the side edge portion of the web.
Absorbent articles are manufactured in different sizes, such as S size, M size and L size. In this regard, the aforementioned conveyor can convey webs of various sizes by moving the actuator coupled to the nip rollers, and the sensor independently of each other in the web cross direction.
The inventors have discovered that when the size of a web to be being conveyed is changed to a different one, and the actuator and the sensor are independently moved in the web cross direction, and therefore the nip rollers (the actuator) and the sensor may be sometimes misaligned in an inappropriate positional relationship. In this case, the inappropriate positional relationship causes the nip rollers to be rotated by an erroneous amount. To avoid this, the positional relationship between the nip rollers and the sensor needs to be adjusted to a predetermined relationship, which, in turn, requires complicated control for this adjustment. It is desirable to provide a conveyor and a method of manufacturing absorbent articles which are capable of selectively conveying webs of different sizes by changing a passing position of a side edge portion of the web, without having to perform complicated control and/or adjustment.
Under these circumstances, the present invention is aimed to provide a conveyor and a method of manufacturing an absorbent article which are capable of selectively conveying any of webs for two or more sizes by easily changing a passing position of a side edge portion of the web without having to perform complicated control.